<template>
  <div class="spec-preview">
    <img :src="skuImageList[defaultIndex]?.imgUrl " />
    <!-- 给最外层绑定移动事件 -->
    <div class="event" @mousemove="mousemove"></div>
    <div class="big">
      <img :src="skuImageList[defaultIndex]?.imgUrl " ref="bigImgEle"/>
    </div>
    <div class="mask" ref="maskEle"></div>
  </div>
</template>

<script>
export default {
  name: "Zoom",
  props: ["skuImageList"],
  data() {
    return {
      defaultIndex: 0
    }
  },

  methods: {
    //实现放大镜
    mousemove(e){
      //计算鼠标到盒子边缘的距离
      const orterDistance = {
        x: e.offsetX,
        y: e.offsetY
      }

      //计算蒙版的位置
      const maskDistance = {
        x: orterDistance.x - this.$refs.maskEle.offsetWidth/2,
        y: orterDistance.y - this.$refs.maskEle.offsetHeight/2
      }

      //临界值判断
      if(maskDistance.x < 0) {
        maskDistance.x = 0
      }else if(maskDistance.x > e.target.clientWidth - this.$refs.maskEle.offsetWidth){
        maskDistance.x = e.target.clientWidth - this.$refs.maskEle.offsetWidth
      }else if(maskDistance.y < 0){
        maskDistance.y = 0
      }else if(maskDistance.y > e.target.clientHeight - this.$refs.maskEle.offsetHeight){
        maskDistance.y = e.target.clientHeight - this.$refs.maskEle.offsetHeight
      }


      //赋值
      this.$refs.maskEle.style.left = maskDistance.x + "px"
      this.$refs.maskEle.style.top = maskDistance.y + "px"

      //移动大图
      this.$refs.bigImgEle.style.left = - 2*maskDistance.x + "px"
      this.$refs.bigImgEle.style.top = - 2*maskDistance.y + "px"

    }

  },


  mounted() {
    //自定义事件接收下标改变大图片
    this.$bus.$on("changeBigImg" , (value) => {
      this.defaultIndex = value
    })
  },

};
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>